甲玛铜多金属矿是西藏冈底斯成矿带中东段勘查程度最高、成矿元素与矿体类型复杂的超大型斑岩-矽卡岩型矿床.前人在控岩-控矿构造、矿床地质、地球化学、矿床模型等方面已经完成了大量的研究工作,但对于矿床成矿机制研究方面尚存不足,特别是流体、成矿物质的来源方面欠缺系统的研究工作和对资料的全面梳理.文章在大量阅研和总结前人研究资料的基础上,以矿区16号勘探线作为典型剖面开展了氧同位素填图,同时对硫同位素进行了必要的样品补充采集.通过综合研究,有证据表明甲玛矿区深部隐伏斑岩体存在岩浆流体的出溶,在此基础上,氢、氧同位素组成表明矿化由早到晚演化过程中,流体由岩浆水向大气降水增加方向演化;同时,氧同位素填图以及流体包裹体平面均一温度分布确定成矿流体源位于矿区zk1616~zk3216一带.此外,S、Si同位素组成均表明了矿区成矿物质主要来源于成矿岩浆岩,而铅同位素的研究进一步说明成矿物质主要来源于冈底斯后碰撞环境下因地壳减薄、地幔上涌导致的壳幔混合作用.文章依据地球化学的研究成果,探讨矿床流体、成矿物质的来源,为甲玛矿床成因、成矿机制研究夯实基础.
Located in central eastern Gangdise metallogenic belt,the Jiama polymetallic copper deposit is a giant porphyry-skam type deposit characterized by the highest level of exploration and complex ore-forming elements and ore body types.Previous researchers have already completed a lot of research work,which includes rock and ore-controlling structure,deposit geology,geochemistry,model of the deposit and some other aspects; nevertheless,researches on metallogenic mechanism of the deposit remain very insufficient.The source of fluid materials lacks systematic study and the information lacks comprehensive rearrangement.Based on reading lots of research reports and summarizing the data obtained by previous studies,the authors carried out the oxygen isotope mapping and collected necessary additional samples of sulfur isotope along No.16 exploration line which served as the typical cross section.A comprehensive study reveals that there existed magmatic fluid exsolution in the deep-seated porphyry concealed under the Jiama ore district,and hydrogen and oxygen isotopic combination suggests that from the early stage to the late stage of mineralization,fluid evolved gradually from the magmatic water to the atmospheric water.In addition,the oxygen isotope mapping and the distribution of uniform temperature plane of fluid inclusions demonstrate that the source of oreforming fluids was located around drill hole zk1616~zk3216 in this ore district.S,Si isotopic combination implies that the materials were mainly derived from the ore-forming magmnatic rocks,and the study of lead isotope further indicates that the metallogenic materials came from the collision environment in Gangdise; the crustal thinning and the crust-mantle upwelling led to the mixture of the crust and the mantle.Based on the study of geochemistry,the authors probed into the source of fluid and metallogenic materials,and the results obtained have laid a solid foundation for the study of the genesis and the metallogenic mechanism of the Jiama ore deposit.